[WebUI] Cleanup of css files

 * Consistent indent and line endings
 * Remove unused redo icon
 * Minify extensions css
[WebUI] Flake8 files

 * Does not pass cleanly due to camelcase function names and __request__ global.
Flake8 core files
Replace try statement for LT_TORRENT_STATE_MAP lookup
Remove obsolete set_state method
Replace use of status key 'tracker' with 'tracker_host' in UIs

 * Status key tracker can be empty so use tracker_host instead, also tracker_host
   is nicely formatted.
 * Remove unneeded tracker_host string from tracker_status.
[WebUI] Fix tracker_host mistake
Fixed bug in Blocklist WebUI pref page
[#1310] [Notifications] Add webui prefs page
[Notifications] Small layout fixes for web page and version bump